1. Field of the Invention
The present invention relates to a phase adjusting device for performing phase (timing) adjustment of a pulse used for imaging in a digital camera, and a digital camera incorporating the phase adjusting device. The present invention also relates to a phase adjustment driving device, and a phase adjusting method. The main pulse which is a target of the phase adjusting technique of the present invention is at least one of a peak sample pulse for detecting a level of an imaged signal output from an imaging element, a reference sample pulse for detecting a signal level that becomes a reference of correlated double sampling, and an AD clock signal output to an external AD converter.
2. Description of the Related Art
In digital cameras (digital still camera, digital video camera, portable telephone with camera, and the like), an analog imaged signal that is imaged by an imaging element such as a CCD and a MOS sensor is converted to a digital imaged signal, and such a digital imaged signal is recorded after being subjected to a predetermined signal process. The pulse for driving the imaging element, the pulse for detecting the signal level, and the like are required to image a subject with the imaging element. Since the phases of such pulses is subject to variations originating from manufacturing, it is difficult to adjust the pulse phase when designing hardware. Thus, a technician performs phase adjustment after manufacturing, stores information indicating the adjusted phase in a storage region, and thereafter, users reads out the phase information from the storage region in actual use to set an optimum phase.
A technique of retrieving mostly a noise component with the exposure time at a minimum and adjusting the phase under the condition the high frequency component (noise component) becomes a minimum is conventionally known (see Japanese Laid-Open Patent Publication No. 2005-151081).
In the field of digital cameras, the system incorporating the phase adjusting device is sometimes changed in a wide variety of ways. Particularly, in the field of medial cameras and the like, the imaging element is sometimes replaced after the digital camera is manufactured. If the system incorporating the phase adjusting device or the imaging element differs, the phase of the pulse for driving the different system or element obviously differs, and thus the phase must be readjusted. However, changing of the system incorporating the phase adjusting device and replacement of the imaging element are difficult to be rapidly and easily performed if a technician has to readjust the phase manually.
Although the pulses to be adjusted are of a plurality of types, the optimum phase is obtained with the same method for all the pulses without taking the characteristics of each pulse into consideration in the Japanese Laid-Open Patent Publication mentioned above, and thus the precision is not very high.
The optimum phase also changes depending on external factors such as change in temperature and voltage, and thus it is desirably adjusted every time photographing conditions change. However, the pulse phase adjustment of the prior art is assumed to be performed in time of factory shipment and due consideration has not been given to a case of adjustment being performed by the user, where the adjustment is actually troublesome when performed by the user.